The present invention relates to reinforcing materials used in flexible "V"-type belts and the methods for producing same. More particularly, the invention relates to a V-belt construction having, as one component thereof, a fiber-loaded seamless industrial fabric produced from the treatment of a non-woven fabric, whereby the fabric has a high percentage of either "chopped" or "staple length" fibers oriented in the "cross-machine" (fill) direction. i.e., perpendicular to the non-woven fabric length.
Conventional raw edge V-belts produced from fabrics containing chopped fibers, as well as large "full-wrapped" V-belts, are typically manufactured by combining the chopped fibers with a rubber compound, milling and then calendering the resultant mixture to form fiber-loaded sheets which are used to form the inside portion of the belt--that is, the portion which undergoes considerable stress (both axially and longitudinally) during normal use in, for example, high speed pulley arrangements. Almost all conventional V-belts also utilize one form or another of a strength member incorporated in the body of the belt.
It has long been known that the addition of chopped fiber adds stability widthwise and allows the belt to flex and elongate in the lengthwise direction. Known chopped fiber constructions are also intended to hold the belt in a "V" shape, and to thereby reduce abrasion at the contact points between the belt and any associated pulleys or other friction surfaces.
A critical limitation of conventional prior art V-belt constructions is that the equipment used to compound and calender the rubber/fiber mixtures are not generally capable of forming sheets having a chopped fiber concentration of over 10% by weight. Although it is known that a rubber to fiber ratio of over 25% would considerably improve belt stability and increase belt life, the conventional compounding methods have not been capable of achieving such a high percentage of fiber concentration.
In addition, conventional compounding methods are not capable of orienting the fibers in the cross-machine direction in sufficiently high concentrations to avoid cutting and splicing the fiber-loaded sheets. For example, a known method used by V-belt manufacturers to compound rubber and thereafter orient chopped fibers in a widthwise direction includes the following basic steps. First, the chopped fibers (approximately 1/4 inch in length) are added to a base rubber composition with additional mixing to break the fibers into individual components. The composition is then processed on a rubber mill and "slabbed" (generally in 1/2 inch thick sheets) which are then calendered to sheets approximately 60 inches wide and 0.060 inches thick. The calendering step orients 60% to 80% of the chopped fibers in the lengthwise direction of each sheet. The 60 inch sheets are then cut to 41 inch lengths and combined by splicing individual sections crosswise to form a continuous roll (generally 41 inches wide) for belt makeup purposes. This step is necessary in order for 80% of the fibers to be oriented in the crosswise direction relative to the longitudinal axis of the finished V-belt.
Likewise, a known method for manufacturing "full-wrapped" V-belts consists of the following steps. First, a layer of cushion fabric, commonly referred to as a "bias fabric", is placed on the belt makeup drum followed by layers of a fiber-loaded sheet previously calendered (as described above) to a specified thickness. A continuous strength element (generally consisting of one or more rubberized cord fabrics) is placed on top of the calendered sheets, followed by a rubberized laminate fabric. The V-belt is then slit to the desired size and shape and "wrapped" with a bias fabric (generally 45.degree. or more) by one ore more complete wraps. The bias fabric overlaps on the underside of the narrow portion of the V-belt and the resultant "wrapped" construction is then cured in a conventional oven at a temperature and for a period of time sufficient to vulcanize the rubber components, thereby forming a cohesive structure.
Although conventional prior art V-belt constructions are acceptable for most moderate stress applications, they suffer from having a limited amount of chopped fiber within the base rubber compound and a lack of fiber orientation in the cross-machine (widthwise) direction. V-belts having a high percentage (i.e. greater than 10%) of fiber in the widthwise direction are, in fact, very difficult to manufacture because of the natural tendency of the fibers to become oriented in a lengthwise direction (relative to the longitudinal axis of the belt) during milling or calendering operations. Such limitations reduce overall belt stability and life span, particularly in high stress applications. In addition, conventional prior art V-belt constructions are relatively expensive, particularly in the larger sizes, due to the additional cutting and splicing steps required to achieve a higher percentage of fibers in the cross-machine direction.
Thus, it is an object of the present invention to provide an improved V-belt construction having a higher percentage of stability-improving fibers (i.e. more than 10 percent) incorporated into the belt in an oriented manner to provide sufficient flexibility in the lengthwise direction, but good stability widthwise.
It is a further object of the present invention to provide for a method of manufacturing a "seamless" V-belt reinforcing fabric having a higher percentage of stability-improving fibers oriented in a crosswise direction.
It is still a further object of the present invention to provide a simplified and improved V-belt having high flexibility but greater stability and a longer life-span than conventional constructions.
These and other objects of the invention will become evident from the detailed description, drawings and appended claims.
It has now been found that the foregoing objects regarding overall strength, utility and life-span of V-belts can be accomplished by a unique construction whereby a seamless, i.e., endless and non-spliced, fabric is produced from a non-woven fabric having an increased percentage of either chopped or "staple length" fibers oriented perpendicular to the non-woven fabric length. More particularly, it has now been found that the application of solvent and rubber compositions to the non-woven fabric by way of an initial impregnation and a "re-impregnation" of the fabric, followed by an expansion of the fabric, permits the fibers to be reoriented in the crosswise direction while in a "solvated state" during a subsequent tentering operation. Thus, exemplary V-belt constructions in accordance with the present invention contain a higher percentage of stability-improving fibers incorporated into the belt in an oriented manner to thereby provide sufficient flexibility in the lengthwise direction, but good stability widthwise. It has also been found that both conventional "chopped" fibers (usually about 1/4 inch in length) and "staple length" fibers may be used in fiber-loaded non-woven fabrics and V-belt constructions according to the invention.
The staple length fibers may be from 1/4 inch to 6 inches, preferably 1 inch to 11/8 inches.
The fibers may be cotton, polyester, nylon, nomex, kevlor, rayon or blends of two or more of these fibers.